The determination of the feed rate which must be variably established in successive stages of a given grinding operation, i.e. in transient periods which are immediately after commencement and immediately before the ending and in an intermediate stage in which the grinding load is constant, has been a problem in conventional electrochemical-grinding practice inasmuch as each determination is entirely left to the judgment of the operator based on his experience. Thus, accomplishing a given operation in the shortest total grinding time and with the best finishing quality has essentially required a high degree of operator skill.